1. Field of the Invention
The present invention relates to orthopedic prostheses and, particularly, to tibial prostheses.
2. Description of the Related Art
Orthopedic prostheses are commonly utilized to repair and/or replace damaged bone and tissue in the human body. For example, a knee prosthesis may be implanted during a total knee arthroplasty to replace damaged or destroyed bone in the tibia and/or femur and to recreate the natural, anatomical articulation of the knee joint. A femoral prosthesis may be shaped to replicate one or both of the natural femoral condyles. After resecting the distal end of the femur, one side of the femoral prosthesis is secured to the bone stock of the femur and the opposing side of the femoral prosthesis is configured for articulation against a tibial prosthesis.
A tibial prosthesis may include a first, articulating component having a concave condylar portion configured for articulation against the femoral prosthesis. The articulating component of the tibial prosthesis may be secured to a tray component that has an opposing side for securing the tibial prosthesis to the bone stock of a resected proximal tibia. By securing the articulating component of the tibial prosthesis to the tray component to prevent translation and rotation of the articulating component relative to the tray component, a fixed bearing tibial component is created. The articulating component of the tibial prosthesis may be made from a polymer to facilitate articulation with the femoral component, while the tray component of the tibial prosthesis may be made from a metal to provide additional strength and rigidity to the tibial prosthesis.
When implanting a fixed bearing tibial prosthesis during a total knee arthroplasty, a surgeon attempts to balance the effects of several competing factors. First, the surgeon may attempt to ensure that the tibial prosthesis is implanted in its most desirable rotational position with respect to the resected proximal tibia. In setting the most desirable rotational position of the tibial prosthesis with respect to the resected proximal tibia, the surgeon may attempt to maximize tibial bone coverage and/or position the tibial prosthesis in a rotational position that also does not overhang, i.e., extend outward beyond, the resected proximal tibia. Undercoverage of the resected proximal tibia is associated with concerns of subsidence of the tibial prosthesis over time, whereas overhang is associated with concerns of soft tissue impingement. By implanting the tibial prosthesis in the most desirable rotational position with respect to the resected proximal tibia, the likelihood of subsidence, instability in the tibia, and soft tissue impingement are reduced.
Alternatively, the surgeon may attempt to position the tibial prosthesis on the resected proximal tibia at a position in which it is most desirably rotated with respect to the femoral prosthesis. Thus, the surgeon would implant the tibial prosthesis at a position that provides the best conformity between the femoral prosthesis and the tibial prosthesis during knee articulation. By implanting the tibial prosthesis in the most desirable rotational position with respect to the femoral prosthesis, potential difficulties in balancing the knee joint and in creating proper varus/valgus alignment may be avoided. However, implanting the tibial prosthesis at a position in which it is in the most desirable rotational position with respect to the femoral prosthesis may not result in the implantation of the tibial prosthesis in the most desirable rotational position with respect to the resected proximal tibia.
In order to address these concerns, mobile tibial bearing prostheses have been developed. However, for certain patients, the use of a mobile tibial bearing prosthesis may be contraindicated.